In the related art, in a power conversion device which supplies electrical power to, for example, an LED element as a load, an AC power supply voltage is converted to a DC voltage, the DC voltage is converted to a predetermined output voltage by an output conversion circuit having a switching element which turns the DC voltage on and off at constant frequency, supplies the converted output voltage to the LED element, and lights up the LED element.
In such a power conversion device, it is controlled such that an output current which is output to the LED element is detected, an ON time of the switching element of an output conversion circuit is varied according to the detected output current, and the LED element is supplied with a constant output current.
For example, when the power conversion device is used in common by a plurality of types of loads of which the number of LED elements is different, if a load using a certain number of LED elements is set to the reference, the ON time of the switching element is controlled to be short, since it is preferable that the output voltage which is output from the output conversion circuit be small, as the number of LED elements is small. However, since the switching element has a property in which a power loss in the switching element is increased, as the ON time of the switching element becomes short, there is a problem in that power conversion efficiency is decreased.
An object of the embodiments is to provide a power conversion device and a lighting device in which high power conversion efficiency is maintained regardless of a value of an output voltage which is output to a load.